biology

Relaxin-3

Relaxin-3 is a biology topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Relaxin-3 rather than just read about it. In short: Relaxin-3 is a neuropeptide that was discovered in 2001, and which is highly conserved in species ranging from flies, fish, rodents and humans. Relaxin-3 is a member and ancestral gene of the relaxin family of peptides, which includes the namesake hormone relaxin (designated 'H2 relaxin' in humans) which mediates peripheral actions during pregnancy and which was found to relax the pelvic ligament in guinea pigs almo…

Key takeaways

Relaxin-3 belongs to biology; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Relaxin-3 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Relaxin-3 from memory before moving on to harder problems.

Reference excerpt

Relaxin-3 is a neuropeptide that was discovered in 2001, and which is highly conserved in species ranging from flies, fish, rodents and humans. Relaxin-3 is a member and ancestral gene of the relaxin family of peptides, which includes the namesake hormone relaxin (designated 'H2 relaxin' in humans) which mediates peripheral actions during pregnancy and which was found to relax the pelvic ligament in guinea pigs almost a century ago. The cognate receptor for relaxin-3 is the G-protein coupled receptor RXFP3 (relaxin family peptide 3 receptor), however relaxin-3 is pharmacologically able to also cross react with RXFP1 and RXFP3 (although the physiological relevance of such interactions, if they exist endogenously, are currently unknown).

Structure Relaxin-3 consists of 51 amino acids in humans which are arranged into a two-chain structure (designated the A-chain and B-chain). There are three disulfide bonds (two interchain, one intrachain), with the residues that mediate binding to/activation of RXFP3 residing within the B-chain. At translation, pro-relaxin-3 also contains a C-chain (in between the A and B-chains) which is removed via protolytic cleavage to form the mature neuropeptide.

Distribution Relaxin-3 is mostly expressed within neurons of the brain, where it is packaged into dense cored vesicles and trafficked along axons where it can be detected in presynaptic vesicles before release onto target neurons, characteristic of a neurotransmitter. The largest number of relaxin-3-positive neurons in the rodent brain are within a region of the pontine brainstem known as the nucleus incertus, while smaller populations are present within the pontine raphe, periaqueductal grey, and an area dorsal to the substantia nigra. From these centres, relaxin-3 innervates a broad range of brain regions which are also rich in RXFP3 mRNA/binding sites, including the extended limbic system and the septohippocampal pathway.

Function The broad distribution of relaxin-3 fibres/RXFP3 within several key neuronal circuits suggests an ability to modulate a broad range of behaviours. This has been confirmed in a growing number of rodent studies, which demonstrate relaxin-3 is able to modulate arousal, the response to stress, feeding/metabolism and memory; and likely plays a role in the generation/regulation of hippocampal theta rhythm.

Relevance to human disease Neuropeptides such as relaxin-3 are attracting increasing interest as targets for the pharmacological treatment of a range of neuropsychiatric diseases. Due to the ability of relaxin-3 to modulate neuronal processes/behaviours such as mood, stress responses and cognition, which are often aberrant in mental illnesses, considerable potential exists for the development of relaxin-3-based drugs to therapeutically treat depression and other mental illnesses.

See also Relaxin family peptide hormones Insulin/IGF/Relaxin family Relaxin Relaxin/insulin-like family peptide receptor 1

References

Illustrations

Worked examples

Example 1 — a first encounter with Relaxin-3

Start with the simplest possible case. Write down what Relaxin-3 claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In biology, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Relaxin-3 before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Relaxin-3 ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Relaxin-3

In research: Relaxin-3 appears in biology research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Relaxin-3 in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Relaxin-3 is common in secondary-school and first-year university syllabi. It links to neighbouring topics Neuropeptides, so understanding it makes those chapters shorter.
In everyday life: Look for Relaxin-3 outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Relaxin-3 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Relaxin-3 means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Relaxin-3 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Relaxin-3 in simple terms?

Why does Relaxin-3 matter?

Because it connects several biology ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Relaxin-3?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Relaxin-3.